拦截过滤器模式(Intercepting Filter Pattern)用于对应用程序的请求或响应做一些预处理/后处理
定义过滤器,并在把请求传给实际目标应用程序之前应用在请求上
过滤器可以做认证/授权/记录日志,或者跟踪请求,然后把请求传给相应的处理程序
拦截过滤器模式涉及以下实体:
- 过滤器(Filter) - 过滤器在请求处理程序执行请求之前或之后,执行某些任务。
- 过滤器链(Filter Chain) - 过滤器链带有多个过滤器,并在 Target 上按照定义的顺序执行这些过滤器。
- Target - Target 对象是请求处理程序。
- 过滤管理器(Filter Manager) - 过滤管理器管理过滤器和过滤器链。
- 客户端(Client) - Client 是向 Target 对象发送请求的对象。
实现
1、 定义类FilterChain、FilterManager、Target、Client作为表示实体的各种对象;
2、 定义类AuthenticationFilter和DebugFilter表示实体过滤器;
3、 定义类InterceptingFilterDemo使用Client来演示拦截过滤器设计模式;
范例
1. 创建过滤器接口 Filter
Filter.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public interface Filter {
public void execute(String request);
}
2. 创建实体过滤器
AuthenticationFilter.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public class AuthenticationFilter implements Filter {
public void execute(String request){
System.out.println("Authenticating request: " + request);
}
}
DebugFilter.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public class DebugFilter implements Filter {
public void execute(String request){
System.out.println("request log: " + request);
}
}
3. 创建 Target
Target.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public class Target {
public void execute(String request){
System.out.println("Executing request: " + request);
}
}
4. 创建过滤器链
FilterChain.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
import java.util.ArrayList;
import java.util.List;
public class FilterChain {
private List<Filter> filters = new ArrayList<Filter>();
private Target target;
public void addFilter(Filter filter){
filters.add(filter);
}
public void execute(String request){
for (Filter filter : filters) {
filter.execute(request);
}
target.execute(request);
}
public void setTarget(Target target){
this.target = target;
}
}
5. 创建过滤管理器
FilterManager.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public class FilterManager {
FilterChain filterChain;
public FilterManager(Target target){
filterChain = new FilterChain();
filterChain.setTarget(target);
}
public void setFilter(Filter filter){
filterChain.addFilter(filter);
}
public void filterRequest(String request){
filterChain.execute(request);
}
}
6. 创建客户端 Client
Client.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public class Client {
FilterManager filterManager;
public void setFilterManager(FilterManager filterManager){
this.filterManager = filterManager;
}
public void sendRequest(String request){
filterManager.filterRequest(request);
}
}
7. 使用 Client 来演示拦截过滤器设计模式
FrontControllerPatternDemo.java
// author: DDKK.COM 弟弟快看,程序员编程资料站(ddkk.com)
// Copyright © 2015-2065 ddkk.com. All rights reserved.
package com.ddkk.gof;
public class InterceptingFilterDemo {
public static void main(String[] args) {
FilterManager filterManager = new FilterManager(new Target());
filterManager.setFilter(new AuthenticationFilter());
filterManager.setFilter(new DebugFilter());
Client client = new Client();
client.setFilterManager(filterManager);
client.sendRequest("HOME");
}
}
编译运行以上 Java 范例,输出结果如下
$ javac -d . src/main/com.ddkk/gof/InterceptingFilterDemo.java
$ java com.ddkk.gof.InterceptingFilterDemo
Authenticating request: HOME
request log: HOME
Executing request: HOME